Arrangement for switching in the high frequency machine to frequency transformers



Nov. 10,1931. R. HERZOG 1,830,758 ARRANGEMENT FOR SWITCHING IN THE HIGH FREQUENCY MACHINE TO FREQUENCY TRANSFORMERS Filed Jan. 6, 192a mvEnTar? Robert Herzog 59 Patented Nov. 10, 1931 UNITED STATES PATENT orricr.

ROBERT HER-ZOG, OF BER-LIN, GERMANY ARRANGEMENT FOR SWITCHING IN THE HIGH FREQUENCY MACHINE TO FREQUENCY TRANSFORMER-S Application filed January 6, 1928, Serial No. 244,967, and. in Germany January 6, 1927.

When a static frequency transformer is set into operation, especially in such cases where the multiplying frequency is obtained directly from the fundamental frequency by means of A. C. saturating circuits, it has been found necessary to guard against high initial selfinductance of the transformers, as the watt capacity of the machine used for supplying the transformer may not be sufficient to supply the necessary magnetizing current. This can be accomplished for instance, by a partial short circuiting of the transformer windings.

As soon as the high magnetizing current (that is,'the resonance of the machine) is secured, the short circuit may be immediately removed without changing the working condition of the arrangement. This procedure is called the impulsing of the frequency transformer and is made more apparent by the following theoretical discussion. This impulsing of the transformer is necessary on account of the disturbing influence of the insufiicient saturation of the iron core when the current has not yet been built up to its proper value, such'as is the case during the starting period. By proper means for producing a temporary current impulse, it is possible to overcome the high starting self inductance and allow the current to readily build up to its proper value without the use of a generator ofa higher k. v. a. output than that necessary for a regular operation.

As is well known, the inductivity of an iron core carrying an electric winding. such as the frequency transformer described in the present invention. changes largely dependent on the value of the current flowing through the core winding. A theoretical curve showing the inductivity as ordinate plotted against the current as abscissa shows a certain initial inductivity for a current equal to zero. When the current is gradually increased, this initial inductivity will at first increase up to a maximum corresponding to the magnetic saturation of the core, and will from then on decrease gradually when the current is furthermore increased. Thus, the inductance is highest at low current; that is, in practical cases during the starting condition. This is due to the fact, as already referred to, that during starting or when no current at all is flowing, the iron core is not yet saturated and accordingly its inductivity will assume a much higher value from that during the operating periods when the core is highly saturated, particularly in the present case of a frequency transformer operating with extremely high saturation. In order to produce a sufiicient starting current to overcome the high inductivity at starting, it would be necessary to provide a supply generator of a comparatively large k. v. a. output. Such generator, however, would not be operated at its best efficiency during the operating periods when only a portion of the starting current impulse is needed. It has, therefore, been proposed in order to use a generator of small output, to produce a strong starting impulse or current kick at the moment the transformer is switched in, which will act to overcome the temporary high starting inductance and push the current over the peak of'the inductance curve and then allow it to build up to its proper operating value; This starting impulse or current kick may be produced, as mentioned above, by short-circuiting part of the transformer winding whereby the amount of self inductance is decreased.

This short circuiting of the windings of the frequency convertor for the purpose of impulsing has been done up to now by hand, which had the disadvantage that mistakes occurred in carrying out the proper sequence of switching. It has also proved burdensome whenever frequent starting and stopping of such an arrangement was necessary.

According to the present invention the switching sequence for causing impulsing is achieved automatically so that the setting of the arrangement into operation is done by the usual manual operation. According to the invention this is done by including an overload relay with a back contact in the. working circuit of the motor driving the high frequency machine, this operates only after the frequency convertor has been impulsed and the consequent energy consumption begins; in which case also the motor loading current reaches a certain value, the relay operates and thereby controls another relay. This latter relay serves for the purpose of setting the arrangement into operation, that is, making the necessary connections for impulsing, such as short circuiting a part of the frequency convertor windings.

The subject matter of the invention is further illustrated by the accompanying figure.

1 is the driving motor which in this case is shown to be a D. C. shunt motor with a field winding 4; 2 is the high frequency ma chine; and 3 the frequency convertor. The excitation of the hi h frequency machine is omitted for simplicity. The part 6 of the frequency convertor winding 5 serves for short-circuiting for the purpose of impulsing by short circuit; 7 and 8 are a self-inductance and a capacity respectively in the frequency convertor primary circuit. These form, together with the frequency convertor windings, a circuit tuned to the fundamental frequency of the high frequency machine 2. The high fre uency machine itself is connected to a suitable part of coil 7 chosen in such a way that the machine carries only the necessary watt current or loss current required by the maintenance of the oscillations in the primary circuit of the frequency convertor.

There is furthermore connected to the terminals of the frequency convertor a tuning self-inductance 9 and capacity 10 as well as coupling coil 11 which comprise the circuit tunedto the multiplied frequency and serving as the multiplying or impulse circuit. The coupling coil 11 is con led to a working circuit (antenna circuit) y means of coupling coil 12'. V

According to the invention, there is an overload relay 13 in the armature circuit of the driving motor. In the open condition this overload relay has a contact held by the spring 14 which connects another relay 17 with a source of energy 16.

The armature of relay 17 when energized closes the circuits necessary for impulsing, thus in the example shown it short-circuits the impulsing winding 6 of the frequency convertor; 20 is the opposing spring for the armature of relay 17. The set of the arrangement is then as follows:

First, the switch 18 is closed, which connects the field of the motor and simultaneously the source of current 16 may be connected to the control circuit of the relay 17. The winding 6 is thereby short circuited. The next operation closes the switch 19 in the armature circuit of the motor, and sets it into operation. As the winding 6 is short-circuited, the frequency convertor is impulsed. The motor 1 takes up a gradually increasing current until at a certain value of the armature current the relay 13 pulls in, breaks the control circuit of relay 17 so that the latter releases the armature 20 and removes the short circuit of the winding 6. As this occurs after the frequency convertor has been impulsed, the normal operating condition is automatically established.

Having described my invention, what I declare to be new and desire to secure and protect by Letters Patent of the United States is 1. In a high frequency generating system, comprising a high frequency generator, a load circuit of said generator including an iron core frequency transformer operated at high alternating current saturation and having high self inductance during starting and low self inductance during operation, an electric prime mover for said generator, a secondary circuit of said frequency transformer, an electric current supply source for said prime mover, circuit connections between said source: and said prime mover including a relay, and means to decrease the initial self inductance of said transformer at starting, said means being controlled by said relay responsive to starting and running conditions of said prime mover.

2. In a high frequency generator system, comprising a high frequency alternator, a load circuit of said alternator including the winding of an iron core frequency transformer operated at high alternating current saturation and having high self inductance during starting and low selfinductance during operation, an electric prime mover for s. id alternator, a current supply source for said prime mover, circuit connections between said source and said prime mover including an overload relay having contacts operating ata distinct value of the current drawn from said supply source and a second relay controlled by said contacts and shortcircuiting part of said transformer winding (luring starting.

3. In a,- high frequency generating system comprising a high frequency alternator, a load circuit of said alternator including a winding of an iron core frequency transformer operating at high alternating current saturation and having high self inductance during starting and low self inductance during operation, an electric prime mover for said alternator, a current supply source for said prime mover, circuit connections between said source and said prime mover in-- cluding an overload relay having contacts, and a second relay controlled by said contacts for short circuiting part of the windings of said transformer during starting.

In testimony whereof I have afiixcd my signature.

. ROBERT HERZOG.

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